Update 2.07pm: SIPTU has accused Transdev of "pouring fuel on the fire" by threatening to dock a full day's pay.
The union’s divisional organiser Owen Reidy claims the company is developing a new initiative every day.
“It’s quite tragic at this stage,” he said.
“Instead of resolving the thing and instead of getting into the space where we spend the next few days in a room hammering out a deal, Gerry seems to spend his time talking and plotting and planning in relation to counteracting action and pouring fuel on the fire.
“Because all of this is counter-productive, all it does is frustrates his employees even more.”
Earlier: Luas drivers have been warned they will be docked a full day's pay during their four-hour strikes.
Members of the SIPTU trade union will walk off the job again this week in their long-running row over pay - with another six stoppages planned for next month.
The new four-hour strikes mark a departure from the 24-hour stoppages staff have been staging, but many of the new times will coincide with rush hour peaks.
Gerry Madden, managing director of Transdev, which operates the Luas, said that the company cannot allow drivers to think their next wave of strikes will work.
"If we were to just accept four-hour or two-hour or whatever... from Siptu, we have the scenario where, if they chose to, they could service further dates after the 10th of June, because we have dates up to that point, where they decide: 'You know what we'll do, is we'll cause maximum disruption to customers, we'll cause minimum loss of pay, and we'll cause maximum financial hardship to the company," he said.